The invention relates to nonshifting transmissions, especially adapted for use in motor vehicles. In the past, commercial nonshifting transmissions have utilized torque converters having two driven turbines and two reactors, the second of which has variable blade positions (the Buick twin turbine transmission; also see U.S. Pat. No. 2,368,873). Other proposals have also been made for the utilization of planetary gears in nonshifting transmissions utilizing hydraulic couplings, dual mechanical clutches, or centrifugal clutches (see U.S. Pat. Nos. 2,821,869 and 3,215,004). In such prior art nonshifting transmissions, component parts of the planetary gear train have of necessity been connected up to stationary components. According to the present invention, however, a transmission has been provided that is truly differential--that is no component parts are connected up to any members that are stationary with respect to the input and output shafts. Such an arrangement can under some circumstances result in easier holding or braking at stops, less tendency of the vehicle with which the transmission is associated to crawl, less consumption of fuel due to easier idling of the motor, and fuel savings in stop-and-go driving. Also, no power is lost in wasteful restraint, rather it is used in useful opposition and passed along to the output mechanism.
According to one aspect of the present invention, a nonshifting transmission assembly is provided including a first input shaft, a second input shaft, an output shaft, a powered shaft operatively connected to the first input shaft, and first and second relatively movable shaft interconnecting members. Means are provided for transforming rotation of the powered shaft into rotation of the output shaft with a gradually decreasing gear ratio as the speed of rotation of the powered and output shafts increase. The transforming means comprises means interconnecting the first input shaft to the first relatively movable member of the interconnecting means, means connecting the second input shaft to the second relatively movable member of the interconnecting means, and planetary gear means connected solely to the first and second input shafts and the output shaft so that no interconnection with any components stationary with respect to the powered shaft and the output shaft is provided.
The first and second input shafts are coaxial, and the interconnecting means may comprise a torque converter, centrifugal clutch, or even a secondary motor hookup. When a torque converter is utilized, preferably the torque converter includes a powered, input shaft, an output shaft, a pump assembly including a rotatable member having impeller blades, a turbine assembly including a rotatable member having turbine blades, the turbine blades disposed radially outwardly of the impeller blades, and a reactor assembly disposed coaxially with the impeller and turbine blades. The reactor assembly has portions disposed at the same radial position as the radial-most extent of both the impeller and turbine blades, and the output shaft surrounds and is concentric with the input shaft. Utilizing the transmission assembly and torque converter according to the invention, it is possible for the turbine of the torque converter to have substantially the same speed as the pump of the turbine assembly. According to another aspect of the present invention, a nonshifting transmission is provided including a first input shaft, a second input shaft surrounding and concentric with the first input shaft, an output shaft coaxial with the first input shaft, and planetary gear means connected solely to the first and second input shafts and the output shaft, so that no interconnection with any component stationary with respect to the input shafts and the output shafts is provided. In one preferred embodiment, the planetary gear means comprises a first sun gear affixed to the first input shaft, a second sun gear affixed to the second input shaft, a first planetary carrier operatively attached to the output shaft, a first planetary gear set operatively connected to the first planetary gear carrier and said first sun gear, and gearing means interconnecting the second sun gear and the first planetary gear set. The gearing means preferably comprises a combination ring gear and planetary carrier, a second planetary gear set, the planetary carrier of the combination ring gear and planetary carrier carrying said second set and the ring gear of the combination planetary carrier and ring gear being in engagement with the first planetary gear set; a third sun gear affixed to said first input shaft; a third planetary gear set; and a double ring gear, the double ring gear in engagement with both the second and third planetary gear sets.
It is the primary object of the present invention to provide a differential, nonshifting transmission assembly, and associated torque converter. This and other objects of the invention will become clear from an inspection of the detailed description of the invention, and from the appended claims.